I've been running a Megasquirt I (with upgraded firmware) since about 7 years now, and Never had any problems with it. Any issues (not that there's been many) have always been external, related to wires and sensors etc, i.e. things you could mess up with any system.
Support and info on the megasquirt forum is plenty and helpful. I built the thing from a kit, but ready built and tested units are available.
With prices having come down dramatically over the last years, I purchased a wide-band lambda with controller from innovate, just awesome with the autotune feature!!! The engine literally tunes it self to perfection just by driving arround!!
it is not 100% plug and play as I suspect some of the commercial systems are, you will have to do stuff like setting up communication ports on the laptop and configure some firmware and INI files, but it is all explained and quite doable.
Looking at value for money, megasquirt is in my opinion unsurpassed.
